The purpose of this proposal is two-fold: 1) to use a realistic model system to understand the basis for exocytosis particularly as it occurs in synaptic transmission. 2) to incorporate ionic channels that occur in biological membranes into planar phospholipid membranes. The infusion of phospholipid vesicles to planar membranes will be used as a model for exocytosis. The basic questions are: What are the rates of fusion? How does the lipid composition in both the planar membrane and the vesicle affect rates of fusion? How does the surface charge of the membrane and concentration of divalent cations in the aqueous media affect the rate of fusion? The answers to these questions for this system will bear directly on exocytotic processes stimulated by Ca2 ion such as release of neurotransmitter from presynaptic terminals (e.g., neuromuscular junctions) and exocytosis in chromaffin cells of adrenal medulla and islet cells of pancreas. In addition, by first incorporating naturally occurring channels (e.g., acetylcholine receptor from electroplax) into the vesicle, one can reconstitute biological channels into planar membranes via fusion. One can then study channels using electrophysiological techniques in a simple and convenient system. Reconstitution also offers an assay for channels during isolation and purification procedures.